This invention relates to apparatus for sensing sources emitting infrared radiation, and more particularly to multi-aperture sensors placed on projectiles for precisely guiding the projectiles toward such sources.
A number of known systems have been developed to locate and track objects, for example in the precision guiding of munitions fired toward a target. One approach involves single aperture sensors utilizing a single lens to receive and focus incident energy on a plurality of detector elements, for example a quad-detector with four separate elements. The target or infrared energy source is deemed centered when the response of all four detectors is the same. While this system is relatively low cost and affords a narrow acquisition field of view for high center tracking accuracy, it lacks wide acquisition field of view for capture of a target. Further, such a system fails to recognize the presence of two or more targets within its field of view, and therefore steers the munition towards the centroid of multiple targets.
Alternatively, sensor systems utilizing a focal plane array have high center tracking accuracy, in that they can create a real or pseudo image of the target or targets. A disadvantage, however, is that such sensors collectively have a narrow field of view in spite their large number. Moreover, the electronics necessary to process the numerous signals is complex and expensive. For example, a project at the University of Florida involves multiple apertures with fiber optic bundles behind each lens. The fiber optic bundles are brought together and a focal plane array is used to sense their output. However, the bundles require a "training" process involving placement of different potential target shapes and at various temperatures in front of the sensor and storing the pseudo image in computer memory. The needs for high speed computation and memory capacity substantially increase the processor cost.
Therefore, it is an object of the present invention to provide a low-cost detector having a large acquisition field of view, yet with high resolution at the center of the field of view.
Another object is to provide a multi-aperture sensor utilizing multiple lenses, each lens with a single detector, arranged in overlapping fields of view.
Yet another object is to provide a multiple lens sensor in which the fields of view of the lenses are selectively positioned for an optimum overlapping in the center of a composite field of view consisting of the fields of view of all lenses.